Abstract Clinical trials for the treatment of Alzheimer's disease (AD) targeting amyloid have largely failed. Ca2+ dysregulation may be an alternative mechanism. In familial AD (FAD), calcium homeostasis is disrupted by over activation of NMDA (NMDAR) and ryanodine (RYR) receptors leading to increased cytosolic calcium and subsequent cognitive dysfunction and neuropathology. APOE4, a major risk factor for sporadic AD (SAD), also causes Ca2+ dysregulation related to NMDAR/RYR over activation. Dantrolene, a RYR antagonist and clinically available drug, has been shown to mitigate amyloid pathology, neurodegeneration, synaptic and memory loss in a FAD animal model. Our preliminary studies suggested that intranasal dantrolene administration abolished memory loss in 5XFAD mice. Furthermore, dantrolene promoted neuronal differentiation in induced pluripotent stem cells (iPSC) from patients with either SAD with APOE4 or familial AD (FAD) by inhibition of RYR/NMDAR over- activation. Our long term goal is to examine the efficacy of dantrolene to treat AD. The overall objective of this study is to investigate the effects and underlying mechanisms of dantrolene on adult neurogenesis in human and rodent SAD and FAD cells, as well as the effects of intranasal dantrolene administration on adult neurogenesis and cognitive function in AD transgenic mice. Our central hypothesis is that intranasal dantrolene inhibits the excessive activation of RYRs and NMDARs in AD and promotes adult neurogenesis, improved cognitive function and reduced AD neuropathology. We will test the hypothesis by the following specific aims. Specific Aim 1. To determine the effects of dantrolene on RYR and NMDAR expression and on cytosolic, mitochondrial, and ER Ca2+ concentrations and AD biomarkers in AD stem cells using induced pluripotent stem cells (iPSC) from fibroblasts patients with either SAD (APOE4 risk factor) or FAD (PSEN1 mutations), as well as neuroprogenitor cells (NPC) isolated from E4FAD (APOE4+5XFAD) and 5XFAD transgenic Specific Aim 2. To examine the effects of dantrolene on RYR and NMDAR activity, neurogenesis, proliferation, and the cellular function of derived neurons and glia from AD cells. using the same cells as in SA1. Specific Aim 3. To determine the effects of dantrolene on adult neurogenesis, cognitive function, and neuropathology in animal models of AD. We expect that dantrolene will promote adult neurogenesis and restore cognition and reduce AD pathology in AD mouse models by alleviating the excessive activation of RYRs and/or NMDARs, especially with the intranasal approach.